Grip force detection apparatus

ABSTRACT

A grip force detection apparatus for a sheet transport having a gripping mechanism for transporting sheet material past xerographic processing stations. The grip force detection apparatus is arranged to pull sheet material away from the moving gripping mechanism if not properly gripped to effect safe delivery of the sheet material at a feed out station.

United States Patent Edward J. Lavander References Cited [72] Inventor S mm T mm N m m E M m m P L m ae But T e m A mb T e S WW. Dt ESP H 70 N36 U99 HH l2 33 35 8,4, 54 82 0,9, 22 m w r, w k6 y 5M h4.. 9m R a N .Ld D. Pm AF l] l2 22 [l [45] Patented Dec. 2l, 1971 [73] Assignee Xerox Corporation Rochester, N.Y. A

Primary Examiner-Joseph Wegbreit Attorneys-James J. Ralabate, Norman E. Schrader and Melvin A. Klein [54] GRIP FORCE DETECTION APPARATUS mfmennfczm 628.785

SHEET l UF 2 -F/G. J

INVENTOR. EDWARD J. LAVANDER BY I, Mefwm @uw A TTORNE V This invention relates to sheet transports and, in particular, to an improved sheet-handling apparatus for use in xerographic reproduction machines.

. As is generally well known, the feeding of double sheets or skewed sheets through a xerographic reproduction system is frequently the cause of a jam in the sheet transport which ultimately can result in a Gre at a heat-fixing station.

Recently there has been an effort to improve sheet gripping devices which transport sheet metal at very high speeds through the xerographic processing stations. Such a device is described in a copending application Ser. No. 730,465, filed May 20, 1968.

The present invention is concerned with an improved grip force detection apparatus which insures that any sheet or sheets of material conveyed through the xerographic processing stations is properly gripped to e'ect a proper transport and safe delivery to a feed out station and is especially intended as an improvement over the sheet transport of the above-mentioned copending application.

It is therefore an object of this invention to improve the transport of sheet material.

It is another object of the invention to insure the safe transport of any sheet or sheets of material through the processing stations of a xerographic reproduction machine.

It is another object of the invention to remove any sheet or sheets of material not properly gripped during transport prior to the sheet material entering xerographic transfer and fixing stations.

It is another object of the invention to affect shutdown of a xerographic machine in the event that a paper jam occurs in the sheet transport system.

These and further objects and features of the invention are attained by a grip force detection apparatus that senses the force at which sheet material is gripped by a sheet transport gripping device and removes the sheet or sheets of material which are not properly gripped at a predetermined grip force so that the sheet material is prevented from entering the xerographic processing stations. More than this, the grip force detection apparatus generates a signal to machine control to shut down the machine in fail safe condition whereby fires may be prevented from occurring.

For a better understanding of the invention as well as other objects andv further features thereof, reference is had to the following detailed description of the invention to be read in connection with the accompanying drawings wherein:

FIG. l illustrates schematically a xerographic reproduction machine incorporating a grip force detection apparatus according to the present invention;

FIG. 2 is a side view of the grip force detection apparatus of the invention;

FIG. 2A is an enlarged view of the solenoid actuated mechanism for raising and lowering a top drag roll assembly of the grip force detection apparatus; and

FIG. 3 is a plan view of the drag roll assemblies with parts and section to illustrate certain details thereof. Referring now to FIG. l, there is shown schematically a continuous xerographic reproduction machine incorporating a grip force detection apparatus I in accordance with the present invention. The xerographic machine comprises a xerographic drum which rotates in the direction indicated by the arrow to cause the drum .surface sequentially to pass a plurality of xerographic processing stations in the path of movement which may be described functionally as follows:

A charging station A at which a uniform electrostatic charge is deposited on a photoconductive layer of the xerographicdrum.

An 'exposure station B at which a light pattern for an image to be reproduced is projected onto the drum surface to dissipate the charge in a pattern of light and shadow corresponding to the image being reproduced.

A developing station C at which the latent electrostatic image is developed bycascading developer material compris- 2 ing carrier beads and electroscopic toner particles triboelectrically arranged which form a powder image while the electrostatic attraction of the toner particles to the drum surface.

A transfer station D at which the xerographic powder imagey v the drum surface to s` is electrostatically transferred from sheet material which is transported to the transfer station after passing a grip force detection apparatus l0 as will be described more fully hereinafter.

A drum cleaning and discharge station E at which a residual powder image remaining on the drum is cleaned and the drum surface dischargesany remaining charges by a source of illumination. The above processing stations with the exception of the grip force detection apparatus of the present invention are conventional and reference is made to U.S. Pat. No. 3,071,370 issued Jan. l, 1963 for a more detailed description of the above processing stations.

As shown in FIGS. l and 2 to transport a sheet S along its path, a gripping mechanism 33 is actuated upon energization of a sensing switch 40 which is energized by moving a sheet into a slot 44 of a rod 46 of the gripping mechanism by a suitable feed device (not shown). Upon insertion of sheet S into slot 44 and after an appropriate time lapse, a lever 47 moves cam elements 48 which are .moved pivotally about rod 46. Cam elements 48 cause rod 46 to move in a clockwise direction to posih'vely grip the sheet between the upper surface of the rod and the under surface of extending portions of spring stock 49.

A plurality of the gripping mechanism 33 are carried by a chain conveyor which includes a pair of endless roller chains 56 one on each side of the frame which passes from sprocket 58 carried by axle 60 over sprockets 62 and 64 carried by axles 66 and 68, respectively. Axle 66 supports a sheet lift mechanism 70 which serves to bring the 4sheet into contact with the drum at the image transfer station. Sprockets 60 and 64 guide the chains in a path tangential to the surface of the drum. Next the chains are moved past a heat fuser 72 and then through rear feedout drive mechanism 75 where the sheet is released from the gripping mechanism for further transport by a conveyor mechanism (not shown). The chains are then carried over and around a sprocket 77 on axle 78 down to a sprocket 80 secured to a drive shaft 82 and then back to the sprocket 58 on axle 60.

Each set of sprockets is positioned on their respective shaft or axle to space the chains apart from each other by a distance greater than the length of the drum 20 to utilize the full width of the sheet. Chains 56 desirably carry two gripping mechanisms which are spaced equally from each other along the length of the chains. The gripping mechanisms are positioned on the chains at right angles to the path of travel of the chains for movement therewith between a feed-in guide and the rear feed-out drive mechanism 75.

When a sheet is fed into the transport, sensing switch 40 activates a timer of a control circuit which enables a sufficient time to elapse to allow the sheet to be properly seated in the gripping mechanism. After an appropriate time lapse, a signal is supplied to each of a pair of solenoids to close the gripping mechanism 33 thereby securing the sheet for transport through the processing stations.

The above described sheet transport is described more fully in copending application Ser. No. 824,543 tiled May I4, 1969 in the names of E. Burhnam and E. Lavander and reference is made thereto for a more detailed description of the apparatus of the transport.

In accordance with the present invention, sheet material transported by the gripping mechanism 33 is conveyed past grip force detection apparatus 10 which insures that sheet material being conveyed toward the transfer station and fuser is properly gripped. Thus, if a sheet is skewed or if more than one sheet is fed into the gripping mechanism, the sheet material is removed and the machine shut down in fail safe condition .a8 will become more apparent. Referring now to FIGS. 2, 2A, and 3, grip force detection apparatus 10 comprises an upper roll drag assembly 101 and a lower roll drag assembly 103.

Upper roll assembly 101 is movable into and out of the sheet path to contact the lower xed roll assembly 103 in timed relation to the movement of the gripper mechanism. When the gripper mechanism passes upper roll assembly 101 is held out of the path by a spring 105 until such time as the leading edge of the gripper mechanism engages a lever 110 which serves to energize a switch 112. When energized, switch 112 actuantes a solenoid SOL1 which is connected to a bracket member by a spring member 116. Bracket member 115 is carried by a rod 118 which also carries upper roll assembly 101i. When sole-- noid SOL-1 is actuated, upper roll assembly 101 is caused to pivot on an axis through rod 118 against the action of spring 105 into contact with the sheet being moved and lower roll as sembly 103 thereby applying a grip force test as will become more apparent.

As best shown in FIG. 12, it will be noted that a latch member 120 engages a roller 119 on lever 110 when the lever is depressed to hold the lever down insuring that the upper roll assembly remains in the operative position in contact with sheet material and lower roll assembly 103 for a predetermined time. When gripping mechanism 33 approaches transfer station D, the mechanism engages a lever 121 of the lift mechanism 70 which lever has a cable link 122 extending to latch member 120 so as to exert a pulling force on the latch member'when lever ll21 is pivoted. By this arrangement, lever 110 is free to return to its original position opening switch 1 12 and deenergizing solenoid SOL-1.

Upper roll assembly lOl and lower roll `assembly 103 have the same structure which is shown more clearly in FIG. 3 and thus only one of the roll assemblies need be described. As shown in FIG. 3, the roll assembly comprises a shaft member 124 adapted to be supported in a bracket by any suitable means such as lock nuts on the ends. Carried on the shaft member is a tubular member 130 which is received on a bearing member 132 positioned on the central portion of shaft member 124 in abutting relationship with shoulder portion 134 of the shaft member. At one end of the tubular member and bearing member is a D washer member 136 which is urged into contact with the tubular member and bearing member by a spring pressure adjustment member 138 which in tum is engaged by another washer member 140 which in turn is engaged by an adjusting nut 142. By this arrangement, tubular member 130 is allowed to rotate relative to the shaft member 124 through the action of the bearing member 132 until the action of the spring pressure acts to restrain rotation. lt will now be appreciated that by turning the adjusting nut 142, itis possible to vary the tension on the spring pressure adjustment member 138 to vary the ease with which the tubular member may be rotated relative to shaft member 124. lt will be further appreciated that if the tubular member is allowed to rotate relative to the shaft member then the sheet material being carried by the gripper mechanism will be allowed to pass along the sheet path. On the other hand, if the tubular is locked or difficult to rotate, the roller assemblies 101 and 103 will act as a drag force to restrain the sheet material from being moved by the gripper mechanism. ln this manner, sheet material which is skewed or not gripped well by the gripping mechanism will be pulled from the gripping mechanism while the gripping mechanism continues along the sheet transport path. When this occurs, the sheet material is still in contact with switch 40 which will not time out and a signal will be supplied to machine control to shut down the machine at which time the sheet material can be removed from the roll assemblies 101 and 103.

In operation, the gripping mechanism carrying sheet material passes through grip force detection apparatus when upper roll assembly 101. is in raised position due to the action of spring 105. When the gripping mechanism contacts lever 110, switch 112 is closed causing solenoid SOL-1 to be actuated and upper roll assembly 101 to be pivoted downwardly against the action of spring 105. When this occurs a grip force test is applied to sheet material conveyed due to the varying forces that may be exerted by the roll assemblies 101 and 103.

After the grip force test, the switch 112 is deenergized by the action of cable link 122 on latch member 120 which holds this switch closed thereby releasing the upper roll assembly which is returned to the raised position by spring action.

It will be appreciated that various grip forces can be utilized depending upon the thickness of sheet material for reproducing the copies and other conditions such as the sheet transport speed and so forth. To accommodate these different conditions as well as the different grip forces to be detected, it will be noted that by simply turning the adjustment member 142, it is possible to vary the force on the spring pressure adjusting member 138 and D washer 136 and tubular member 130. By this arrangement, the different grip forces of the gripper mechanism on the sheet material can be tested. Where the grip force is insuicient, the sheet material will be removed by the grip force detection apparatus.

Above is described a grip force detection apparatus which insures that sheet material conveyed through xerographic processing stations is properly gripped to effect a safe delivery through the fusing station to the feed out station. lt will be appreciated that this apparatus contributes to the overall reliability of a reproduction machine.

What is claimed is:

l. In a sheet-conveying apparatus in which a gripper mechanism is adapted to carry sheet material from a sheetfeeding station to a sheet delivery station an improved sheet grip force detection apparatus comprising rst roller means disposed in a sheet path adjacent to said sheet feeding station,

second roller means disposed in a sheet path operatively movable at right angles to the sheet path from a first position out of contact with said tirst roller means to a second position in pressure contact with said rst roller means, and

control means associated with each of said roller means to vary the pressure contact of the rollers when in contact with sheet material moved therebetween whereby any sheet or sheets of material improperly gripped by said aforementioned gripper mechanism are pulled out of contact therewith.

2. Apparatus according to claim 1 wherein each of said roller means includes a tubular member rotatably supported on a bearing member and said control means includes a spring member operative to exert a predetermined tension on said tubular member. v

3. In a sheet-conveying apparatus in which a gripper mechanism is adapted to carry sheet material from a sheetfeeding station to a sheet delivery station an improved sheet grip force detection apparatus comprising lirst roller means disposed in a sheet path adjacent to said sheet-feeding station, second roller means disposed in a sheet path in contact with said rst roller means and adapted for movement from a lirst position out of contact with said first roller means to a position in pressure contact with said lirst roller means,

control means associated with each of said roller means to vary the pressure contact of the rollers when in contact with sheet material moved therebetween whereby any sheet or sheets of material improperly gripped by said aforementioned gripper mechanism are pulled out of contact therewith,

wherein each of said roller means includes a tubular member rotatably supported on a bearing member and said control means includes a spring member operative to exert a predetermined tension on said tubular member, and

sensing means for lowering said second roll means in the sheet path after said gripping mechanism is moved therepast and for raising said second roll means after a predetermined interval.

4. Apparatus according to claim 3 wherein said sensing means includes a switch means located in the path of the gripper mechanism so as to be closed by contact therewith and means associated with said switch means for maintaining same closed until said gripper mechanism has conveyed sheet material sufficiently along its path.

l l* i 

1. In a sheet-conveying apparatus in which a gripper mechanism is adapted to carry sheet material from a sheet-feeding station to a sheet delivery station an improved sheet grip force detection apparatus comprising first roller means disposed in a sheet path adjacent to said sheet feeding station, second roller means disposed in a sheet path operatively movable at right angles to the sheet path from a first position out of contact with said first roller means to a second position in pressure contact with said first roller means, and control means associated with each of said roller means to vary the pressure contact of the rollers when in contact with sheet material moved therebetween whereby any sheet or sheets of material improperly gripped by said aforementioned gripper mechanism are pulled out of contact therewith.
 2. Apparatus according to claim 1 wherein each of said roller means includes a tubular member rotatably supported on a bearing member and said control means includes a spring member operative to exert a predetermined tension on said tubular member.
 3. In a sheet-conveying apparatus in which a gripper mechanism is adapted to carry sheet material from a sheet-feeding station to a sheet delivery station an improved sheet grip force detection apparatus comprising first roller means dIsposed in a sheet path adjacent to said sheet-feeding station, second roller means disposed in a sheet path in contact with said first roller means and adapted for movement from a first position out of contact with said first roller means to a position in pressure contact with said first roller means, control means associated with each of said roller means to vary the pressure contact of the rollers when in contact with sheet material moved therebetween whereby any sheet or sheets of material improperly gripped by said aforementioned gripper mechanism are pulled out of contact therewith, wherein each of said roller means includes a tubular member rotatably supported on a bearing member and said control means includes a spring member operative to exert a predetermined tension on said tubular member, and sensing means for lowering said second roll means in the sheet path after said gripping mechanism is moved therepast and for raising said second roll means after a predetermined interval.
 4. Apparatus according to claim 3 wherein said sensing means includes a switch means located in the path of the gripper mechanism so as to be closed by contact therewith and means associated with said switch means for maintaining same closed until said gripper mechanism has conveyed sheet material sufficiently along its path. 